The invention relates to tracking transport vehicles (TV) with the help of radio means, and, more particular, to usage of satellite systems for increasing safety of traffic of the TV by providing the regular automatic monitoring, in real time mode, of precise values of current coordinates of the TV in air, on land and at sea, at standard (normal) conditions of operation (xe2x80x9cMonitoring xe2x80x9d mode) and immediate warning about the precise values of coordinates of sites where extreme situations (emergencies, catastrophes, hijackings etc.) occur (xe2x80x9cEmergencyxe2x80x9d mode ). At present, each of these two problems (xe2x80x9cMonitoringxe2x80x9d and xe2x80x9cEmergencyxe2x80x9d) is dealt with separately within the framework of two independent satellite systems, each of which contains independent complex of equipment of its own, including both the basic equipment (satellites, land data collecting centersxe2x80x94DCC) and sets of many tens of thousand units of on-board equipment (Emergency Position Indicating Radio Beaconsxe2x80x94EPIRB), placed on board air, marine, river and land TV.
International System COSPAS-SARSAT is the only operational specialized independent satellite system for searching the sites of emergencies therefore it was chosen as the prototype for the solution of one aspect of the comprehensive problem. This system provides for the TV to be equipped with EPIRB. Upon manual or automatic activation, these EPIRB radiate, on the specially assigned xe2x80x9cspace emergency frequencyxe2x80x9d 406.025 MHz, the distress calls. Six low orbit earth satellites (LO ES) are used for retransmission of these signals to land DCC (see xe2x80x9cMobile Satellite Communicationsxe2x80x9d, L. M. Nevdyaev, Moscow, MCTI, 1998, pp. 41-44)[1].
However, the latency period of a LO ES occurrence in a zone of a disaster can exceed 1.5 hours. The position of a signaling EPIRB (with accuracy up to 3,000 m) is evaluated by the LO ES onboard processor due to the xe2x80x9cDoppler shiftxe2x80x9d of frequency, which process adds up to 10-15 minutes to the initial delay. Such time consuming search (in principle, bearable in sea or land disasters) basically eliminates possibility of using of this system for searching sites of instant(5-50 sec) air-crashes.
The following attempts to overcome this problem, within the framework of the above system, by preserving the EPIRB intact after destruction of an aircraft have failed:
ejection of EPIRB before a catastrophe takes place, and its soft touchdown by a parachute. The drawbacks: the accuracy and reliability of a precise location of the catastrophe site are drastically reduced, and the cost of EPIRB is considerably increased;
fixation of an extremely durable EPIRB on the outer surface of an aircraft body (i. e. the EPIRB capable to survive the aircraft impact with the ground).
This approach had no success either.
The second important aspect of this comprehensive problemxe2x80x94xe2x80x9cMonitoringxe2x80x9dxe2x80x94is partially solved (for aircraft) by a network of tracking radars, which construction and operation are rather expensive, and also by a network of the ground relay radio stations and rented radio channels of a marine satellite system a INMARSAT covering oceans (see [1], page 69). This solution, for the lack of any better one, was used as the prototype for the solution of the second aspect of the comprehensive problem. To the drawbacks of this prototype one should attribute the considerable costs of construction and operation of a ramified terrestrial network of relay radio stations and high fares for use of radio channels of INMARSAT, which makes this solution compatible, complexity- and cost-wise, with the system of tracking radars. Besides, the INMARSAT geostationary satellites (GS ES), located on a latitude of equator, do not provide the steady connection with air and sea vehicles traveling in a sub-polar zone (there is no direct vision line, and the effect of radio wave xe2x80x9ccurvingxe2x80x9d the Earth, on the operational frequency of this systemxe2x80x941,500 MHz,xe2x80x94is not yet pronounced.
The claimed invention is aimed at the integrated solution of the problem of automatic monitoring of a TV en route (TV tracing) and detection of a TV catastrophe site. The proposed solution can be applied to all kinds of TV, however, since the problem is especially critical in the field of aircraft, this application will consider the practical solution in respect of aircraft.
To deal with the short-lasting (nearly instant) air accidents (catastrophes) the invention offers a new approach eliminating the need to overcome the practically insoluble (by known means) problem of the EPIRB preservation after the aircraft destruction. The invention provides for saving not the EPIRB per se, but for saving the data on precise position of a aircraft fall site, which data the EPIRB will timely transmit before the aircraft destruction.
The invention provides for the development of a satellite system capable of instantaneous action, the response time of which (up to 0.5 sec) is tenfold less than the duration of even most short-lasting (5 sec.) air catastrophes. In such system EPIRB, within few seconds prior to the aircraft destruction but while it is still in air, will manage to transmit, repeatedly and in real time mode, to the air traffic control centers (ATCC), the reliable data on precise values of present coordinates of the aircraft falling trace, up to the moment of the termination of transmission, that is up to the moment of the aircraft destruction.
It is evident, that for implementation of the system of instantaneous response one will have to use the xe2x80x9cfixedxe2x80x9d GS ES which are always ready to prompt retransmission of the emergency information from EPIRB to DCC. The invention provides for the use of five GS ES and the EPIRB linked with them, i.e. the elements constructed and put into the experimental operation in the course of the first modernization of the COSPAS-SARSAT System.
The instantaneous xe2x80x9cactionxe2x80x9d of the on board EPIRB of a new type, is achieved due to incorporation of the following components operating during the flight period:
radio-receiver of signals transmitted by the satellite navigation systems GPS/GLONASS, ensuring instant recording of current values of an aircraft coordinates (latitude and longitude) with accuracy up to 100 m;
powerful transmitter, in stand-by mode, capable of sending a steady and clear distress signal within 0.5 sec without the need of a signal accumulation at a receiving end.
Thus the invention provides for the engagement of GS ES which orbits are fixed at the altitude of some R2=40,000 km, i.e. eleven-fold (11 times) exceeding the distance of reach (R1=3,500 km) of the LO ES within the current COSPAS-SARSAT system. This is why it is, generally, presumed that the output power (P2) of a new type EPIRB should substantially exceed the current output power (P1=5 W) of the operational INMARSAT EPIRB, which might result in drastic increase of the overall dimensions and costs of the EPIRB. One can easily demonstrate that the reasons for such presumption are unsupported. In fact,
P2=P1xc2x7G1/G2xc2x7(R2/R1)2,xe2x80x83xe2x80x83(1)
where G1=2 (3 Db)xe2x80x94antenna gain of LO ES;
G2=50 (17 dB)xe2x80x94antenna gain of GS ES, thus the output power (P2) is equal to;
P2=5xc2x72/50xc2x7(40,000/3,500)2=20 Wxe2x80x83xe2x80x83(2)
As for the overall dimensions and costs of the new powerful EPIRB, the tentative estimations give the figures very close to that of the existing EPIRB within the current COSPAS-SARSAT system based on the LO ES. Thus, the next upgrade of COSPAS-SARSAT system, if based on the present invention, would be, generally, limited to manufacturing and installation, on board the aircraft, of EPIRB as simple and cheap as before. Nevertheless, such upgrade would offer the drastic increase of the system efficiency:
the comprehensive solution of yet unsolved, in principle, problem dealing with the establishment of an air catastrophe site;
reduction of time span (103 to 104 folds) and increase of accuracy (20 to 30 folds) of establishing the sites of aircraft non-destructive emergency landings.
Thus, in accordance with the claimed invention, for the comprehensive solution of the emergency warning problem it is necessary on equip every aircraft with a new type EPIRB. The problem arises concerning the feasibility of equipping many thousand aircraft of a world park with EPIRB constantly xe2x80x9clivexe2x80x9d during each flight, taking into account the fact that the emergency cases, for which EPIRB is designed, are extremely rare. The negative answer to this question becomes obvious, especially, if one recalls that at standard conditions of operation (normal flight) the functional readiness of EPIRB is rarely inspected. Therefore, probability of its reliable operation in extreme conditions can not be high. The invention provides for a combined system which deals with the said problem at no extra costs and in a natural way. For this purpose it is proposed to use same EPIRB for transmission of the alarm signals, and signals for monitoring. In such arrangement the constantly active status of EPIRB in the xe2x80x9cMonitoringxe2x80x9d mode guarantees its functional readiness to be instantly switched to the xe2x80x9cEmergencyxe2x80x9d mode. The selection of contiguous (neighboring) narrow bandwidths of signal transmission within common frequency band (400 MHz) for both modes (xe2x80x9cMonitoringxe2x80x9d and xe2x80x9cEmergencyxe2x80x9d) allows to use in EPIRB the unified broadband transmitter. Thus, in the combined system it is possible to install a single EPIRB, moreover, it is possible to use for retransmission of signals a single GS ES located within the limits of visibility (reach) (see. FIG. 1) and various DCC linked with this GS ES, this arrangement almost twofold reduces costs of the system implementation and substantially increases its reliability. To ensure system operation in a polar zone it is necessary to select such working frequencies, which allow, due to the phenomenon of diffraction (xe2x80x9ccurvingxe2x80x9d the globe), to overcome drawbacks intrinsic to INMARSAT-E system, where the rather high frequency (1,500 MHz) is used. In the proposed solution, for operations in both modesxe2x80x94xe2x80x9cMonitoringxe2x80x9d and xe2x80x9cEmergencyxe2x80x9dxe2x80x94the neighboring frequencies in a common band are selected, the band consists of the frequencies relatively low for satellite systemsxe2x80x94400 MHz, at such band the effect of diffraction is clearly pronounced.